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Abstract:

The present invention relates to a broadband wireless access system
including a femto cell, and more particularly, to a method of low duty
operation in a femto base station. According to one embodiment of the
present invention, in a broadband wireless access system, a method of a
low duty mode operation of a femto base station saving power includes the
steps of determining a low duty mode pattern to be performed by the femto
base station according to a preset reference and performing the low duty
mode operation according to the determined pattern. In this case, the
preset reference can include at least one selected from the group
consisting of a battery level, an available resource status and a
subscriber type of the femto base station.

Claims:

1. A method of a low duty mode operation of a femto base station in a
broadband wireless access system, the method comprising: determining a
low duty mode pattern to be performed by the femto base station according
to a preset reference; and performing the low duty mode operation
according to the determined pattern, wherein the preset reference
includes at least one selected from the group consisting of a battery
level, an available resource status and a subscriber type of the femto
base station.

2. The method of claim 1, wherein if the preset reference includes the
subscriber type, the low duty mode is determined to be a first low duty
mode pattern if the subscriber type is a closed subscriber group (CSG)
open state or a second low duty mode pattern if the subscriber type is a
closed subscriber group (CSG) closed state and wherein the first low duty
mode pattern is set to have a ratio of an available interval for a same
period set greater by a prescribed number than that of the second low
duty mode pattern.

3. The method of claim 1, wherein if the preset reference includes the
battery level or the available resource status, the low duty mode is
determined to be a first low duty mode pattern if the battery level or
the available resource status is equal to or greater than a preset
threshold or a second low duty mode pattern if the battery level or the
available resource status is smaller than the preset threshold and
wherein the first low duty mode pattern is set to have a ratio of an
available interval for a same period set greater by a prescribed number
than that of the second low duty mode pattern.

4. The method of claim 1, further comprising: transmitting at least one
of a cellbar bit set to a value corresponding to the determined low duty
mode pattern and information on the determined low duty mode pattern to a
mobile station.

5. The method of claim 4, wherein the transmission is performed via one
selected from the group consisting of a deregistration command
(AAI_DREG-CMD) message, a sleep response (AAI_SLP-RSP) message, a ranging
response (AAI_RNG-RSP) message, a neighbor advertisement (AAI_NBR-ADV)
message and a super frame header (SFH).

6. The method of claim 4, wherein the cellbar bit is either a closed
subscriber group cellbar bit indicating availability or unavailability
for a service for a random mobile station according to a presence or
non-presence of subscription of a closed subscriber group or a femto
cellbar bit indicating a presence or non-presence of availability for a
service to every mobile station.

7. A method of scanning a femto base station which operates a mobile
station in a low duty mode (LDM) in a broadband wireless access system,
the method comprising: obtaining at least one selected from information
on the group consisting of a cellbar bit set to a value corresponding to
a low duty mode pattern applied to the femto base station, a low duty
cycle ID (LDC ID) having the low duty mode pattern mapped thereto, and
information on the low duty mode pattern; determining a low duty cycle of
the low duty mode (LDM) pattern using the obtained information; and
scanning the femto base station during an available interval (AI) of the
determined low duty cycle.

8. The method of claim 7, wherein the information on the low duty mode
pattern includes at least one selected from the group consisting of a
start frame information indicating a frame number or super frame number
at a timing point that the femto base station starts the low duty mode
operation, a low duty cycle information indicating a length resulting
from adding one available interval (AI) and one unavailable interval
(UAI) in the low duty mode pattern and an available interval information
indicating a length of the available interval.

9. The method of claim 7, wherein the obtainment is performed via one
selected from the group consisting of a deregistration command
(AAI_DREG-CMD) message, a sleep response (AAI_SLP-RSP) message, a ranging
response (AAI_RNG-RSP) message, a neighbor advertisement (AAI_NBR-ADV)
message and a super frame header (SFH) and wherein the selected one is
transmitted by the femto base station or a macro base station including
the femto base station.

10. The method of claim 7, wherein the cellbar bit is either a closed
subscriber group cellbar bit indicating availability or unavailability
for a service for a random mobile station according to a presence or
non-presence of subscription of a closed subscriber group or a femto
cellbar bit indicating a presence or non-presence of availability for a
service to every mobile station.

11. The method of claim 7, wherein the low duty mode pattern is
determined with reference to at least one selected from the group
consisting of a battery level, an available resource status and a
subscriber type of the femto base station.

12. A mobile station, which operates in a broadband wireless access
system, comprising: a processor; and a radio communication (RF) module
configured to transceive a radio signal externally under the control of
the processor, wherein the processor controls the radio communication
module to obtain at least one selected from the group consisting of
information on a cellbar bit set to a value corresponding to a low duty
mode pattern applied to a femto base station operating in a low duty
mode, information on a low duty cycle ID (LDC ID) having the low duty
mode mapped thereto, and information on the low duty mode pattern,
determines a low duty cycle of the low duty mode (LDM) pattern using the
obtained information, and scans the femto base station during an
available interval (AI) of the low duty cycle.

13. The mobile station of claim 12, wherein the information on the low
duty mode pattern includes at least one selected from the group
consisting of a start frame information indicating a frame number or
super frame number at a timing point that the femto base station starts
the low duty mode operation, a low duty cycle information indicating a
length resulting from adding one available interval (AI) and one
unavailable interval (UAI) in the low duty mode pattern and an available
interval information indicating a length of the available interval.

14. The mobile station of claim 12, wherein the information on the
cellbar bit, the information on the low duty cycle (LDC) ID and the
information on the low duty mode pattern are obtained via one selected
from the group consisting of a deregistration command (AAI_DREG-CMD)
message, a sleep response (AAI_SLP-RSP) message, a ranging response
(AAI_RNG-RSP) message, a neighbor advertisement (AAI_NBR-ADV) message and
a super frame header (SFH) and wherein the selected one is transmitted by
the femto base station or a macro base station including the femto base
station.

15. The mobile station of claim 12, wherein the cellbar bit is either a
closed subscriber group cellbar bit indicating availability or
unavailability for a service for a random mobile station according to a
presence or nonpresence of subscription of a closed subscriber group or a
femto cellbar bit indicating a presence or non-presence of availability
for a service to every mobile station.

16. The mobile station of claim 12, wherein the low duty mode pattern is
determined with reference to at least one selected from the group
consisting of a battery level, an available resource status and a
subscriber type of the femto base station.

Description:

TECHNICAL FIELD

[0001] The present invention relates to a broadband wireless access system
including a femto cell, and more particularly, to a method of low duty
operation in a femto base station.

BACKGROUND ART

[0002] A femtocell will be described in brief.

[0003] Femto is a prefix in the metric system, denoting a factor of 10-15.
Hence a femtocell or FBS refers to an ultra-small indoor Access Point
(AP) for low-power home use or office use. Although the term "femtocell"
is sometimes interchangeably used with "picocell", the former is used in
the sense of a more advanced cell. The FBS is a small cellular BS
connected to a broadband router and functions to connect 2nd Generation
(2G) and 3rd Generation (3G) voice and data to a backbone network of a
mobile communication service provider via the Digital Subscriber Line
(DSL).

[0004] An investigation report was released, saying that FBSs would
accelerate 3G proliferation and could be a driving force behind expansion
of indoor coverage. It is forecast that by 2011, there will be 102
million users of users of femtocell products and 32 million APs
worldwide. According to chief analyst of ABI Research, Stuart Carlaw,
"From a technological standpoint, their better in-building coverage for
technologies such as WCDMA, HSDPA and EVDO is an incredibly important
aspect of service delivery. From a strategic and financial standpoint,
the routing of traffic through the IP network significantly enhances
network quality and capacity, and reduces the OPEX that carriers expend
on backhaul."

[0005] Femtocells can expand cell coverage and increase the quality of
voice service. Mobile communication service providers are expecting that
subscribers may be familiar with 3G by providing data service via
femtocells. The femtocells are also called FBSs or femto Base Transceiver
Stations (BTSs).

[0006] In summary, femtocells offer the following benefits.

[0007] 1. Cell coverage improvement

[0008] 2. Infrastructure cost decrease

[0009] 3. New service offering

[0010] 4. Fixed Mobile Convergence (FMC) acceleration.

[0011] One or more femtocells may be grouped on a service basis or
geological area basis. For example, a femtocell group that allows access
to a restricted group of Mobile Stations (MSs) is called a Closed
Subscriber Group (CSG). An FBS allows access only to an MS that has
subscribed to the CSG by checking the CSG Identifier (ID) of the MS.

[0013] FBSs are new network entities added to a legacy network.
Accordingly, the use of FBSs may bring about additions or modifications
to an entire network structure. An FBS may directly access the Internet
and function as a BS. Therefore, the FBS can perform almost all functions
of a macro BS. In addition, the FBS may relay data from the macro BS to
MSs.

[0014] In FIG. 1, the network is configured by adding a Femto Network
Gateway (FNG) to the legacy network. The FNG may communicate with an
Access Service Network (ASN) gateway and a Connectivity Service Network
(CSN). The FNG may use an Rx interface for communicating with the ASN and
an Ry interface for communicating with the CSN.

[0015] An FBS may access directly a Transmission Control Protocol/Internet
Protocol (TCP/IP) Internet and receive a service from the CSN via the
FNG. An MS connected to the FBS may receive services from the FNG or CSN
in relation to IP Multimedia Subsystem (IMS) authentication, etc.

[0016] The FBS is connected to an AP via an R1 interface. This means that
the FBS may receive a downlink channel from a macro BS. The FBS may also
transmit a control signal to the macro BS.

[0017] Femto cells can be classified into the following three types
according to a service provided type (i.e., a provided target, e.g., a BS
subcarrier type).

[0018] 1. Open subscriber group femto cell base station (OSG femto cell
BS): Every mobile station is granted to receive a service provided by a
femto cell.

[0019] 2. Closed subscriber group open femto cell base station (CSG open
femto cell BS): This BS provides all services to a mobile station
registered with a closed subscriber group (CSG). Yet, this BS just
provides a basic service to a non-registered mobile station.

[0020] 3. Closed subscriber group open femto cell base station (CSG open
femto cell BS): This BS provides a service only to a mobile station
registered with a closed subscriber group.

[0021] Generally, in a broadband wireless access system, since a number of
mobile stations are connected to a macro base station, power consumption
of a base station has not been taken into consideration. However, in
femto cell supported environment, the number of mobile stations supported
by one femtocell is limited (e.g., about 5 to 6 mobile stations).
Occasionally, a mobile station maintaining a connection to a femto cell
for specific duration may not exist. If the above-described situations
repeatedly take place, a femtocell continues to provide a prescribed
service to a specific mobile station that does not require the
corresponding service. Accordingly, the demand for overcoming the above
situations (i.e., femto cell BS power saving) is rising.

[0022] Moreover, a mobile station should detect femto cells around to
enter a femto cell within a network. Therefore, a method of facilitating
a mobile station to detect a femto cell around is necessary.

[0023] Besides, a method of reducing interference between a macro cell and
a femto cell by turning off the femto cell is necessary as well.

DISCLOSURE OF INVENTION

Technical Problem

[0024] An object of the present invention is to provide a method of low
duty operation in a femto base station, by which a femto cell can
efficiently operate in a low duty mode in a wireless access communication
system supporting the femto cell.

[0025] Another object of the present invention is to provide a method of
low duty operation in a femto base station, by which a different low duty
mode pattern is applied according to a type of a femto cell.

[0026] Another object of the present invention is to provide a method of
low duty operation in a femto base station, by which a mobile station is
enabled to be implicitly aware of a low duty mode pattern.

[0027] A further object of the present invention is to provide a method of
low duty operation in a femto base station, by which the femto base
station is able to determine a low duty mode pattern to follow according
to one of various conditions.

[0028] It will be appreciated by persons skilled in the art that that the
objects that could be achieved with the present invention are not limited
to what has been particularly described hereinabove and the above and
other objects that the present invention could achieve will be more
clearly understood from the following detailed description taken in
conjunction with the accompanying drawings.

Solution to Problem

[0029] The present invention discloses an efficient low duty mode
operating method of a femto base station to solve the above technical
tasks.

[0030] To achieve these and other advantages and in accordance with the
purpose of the present invention, as embodied and broadly described, in a
broadband wireless access system, a method of a low duty mode operation
of a femto base station saving power according to the present invention
includes the steps of determining a low duty mode pattern to be performed
by the femto base station according to a preset reference and performing
the low duty mode operation according to the determined pattern, wherein
the preset reference includes at least one selected from the group
consisting of a battery level, an available resource status and a
subscriber type of the femto base station.

[0031] Preferably, if the preset reference includes the subscriber type,
the determining step is performed in a manner of determining a first low
duty mode pattern if the subscriber type is a closed subscriber group
(CSG) open state or a second low duty mode pattern if the subscriber type
is a closed subscriber group (CSG) closed state. And, the first low duty
mode pattern is set to have a ratio of an available interval versus a
same time set greater by a prescribed magnification than that of the
second low duty mode pattern.

[0032] Preferably, if the preset reference includes the battery level or
the available resource status, the determining step is performed in a
manner of determining a first low duty mode pattern if the battery level
or the available resource status is equal to or greater than a preset
threshold or a second low duty mode pattern if the battery level or the
available resource status is smaller than the preset threshold. And, the
first low duty mode pattern is set to have a ratio of an available
interval versus a same time set greater by a prescribed magnification
than that of the second low duty mode pattern.

[0033] Preferably, the method further includes the step of transmitting at
least one of a cellbar bit set to a value corresponding to the determined
low duty mode pattern and information on the determined low duty mode
pattern to a mobile station.

[0034] More preferably, the transmitting step is performed via one
selected from the group consisting of a deregistration command
(AAI_DREG-CMD) message, a sleep response (AAI_SLP-RSP) message, a ranging
response (AAI_RNG-RSP) message, a neighbor advertisement (AAI_NBR-ADV)
message and a super frame header (SFH).

[0035] More preferably, the cellbar bit includes one selected from the
group consisting of a closed subscriber group cellbar bit indicating
availability or unavailability for a service for a random mobile station
according to a presence or non-presence of subscription of a closed
subscriber group and a femto cellbar bit indicating a presence or
non-presence of availability for a service to every mobile station.

[0036] To further achieve these and other advantages and in accordance
with the purpose of the present invention, a method of scanning a femto
base station, which operates a mobile station in a low duty mode (LDM),
in a broadband wireless access system including a femto cell according to
the present invention includes the steps of obtaining at least one
selected from information on the group consisting of a cellbar bit set to
a value corresponding to a low duty mode pattern applied to the femto
base station, information on a low duty cycle ID (LDC ID) having the low
duty mode mapped thereto, and information on the low duty mode pattern,
determining a low duty cycle of the low duty mode (LDM) pattern using the
obtained information, and scanning the femto base station in an available
interval (AI) of the low duty cycle.

[0037] Preferably, the information on the low duty mode pattern includes
at least one selected from the group consisting of a start frame
information indicating a frame number or super frame number at a timing
point that the femto base station operates in the low duty mode, a low
duty cycle information indicating a length resulting from adding one
available interval (AI) and one unavailable interval (UAI) in the low
duty mode pattern and an available interval information indicating a
length of the available interval.

[0038] Preferably, the obtaining step is performed via one selected from
the group consisting of a deregistration command (AAI_DREG-CMD) message,
a sleep response (AAI_SLP-RSP) message, a ranging response (AAI_RNG-RSP)
message, a neighbor advertisement (AAI_NBR-ADV) message and a super frame
header (SFH) and wherein the selected one is transmitted by the femto
base station or a macro base station including the femto base station.

[0039] Preferably, the cellbar bit includes one selected from the group
consisting of a closed subscriber group cellbar bit indicating
availability or unavailability for a service for a random mobile station
according to a presence or non-presence of subscription of a closed
subscriber group and a femto cellbar bit indicating a presence or
non-presence of availability for a service to every mobile station.

[0040] Preferably, the low duty mode pattern is determined with reference
to at least one selected from the group consisting of a battery level, an
available resource status and a subscriber type of the femto base
station.

[0041] To further achieve these and other advantages and in accordance
with the purpose of the present invention, a mobile station, which
operates in a broadband wireless access system, according to the present
invention includes a processor and a radio communication (RF) module
configured to transceive a radio signal externally under the control of
the processor. In this case, the processor controls the radio
communication module to obtain at least one selected from the group
consisting of information on a cellbar bit set to a value corresponding
to a low duty mode pattern applied to a femto base station operating in a
low duty mode, information on a low duty cycle ID (LDC ID) having the low
duty mode mapped thereto, and information on the low duty mode pattern,
determines a low duty cycle of the low duty mode (LDM) pattern using the
obtained information, and scans the femto base station in an available
interval (AI) of the low duty cycle.

[0042] Preferably, the information on the low duty mode pattern includes
at least one selected from the group consisting of a start frame
information indicating a frame number or super frame number at a timing
point that the femto base station operates in the low duty mode, a low
duty cycle information indicating a length resulting from adding one
available interval (AI) and one unavailable interval (UAI) in the low
duty mode pattern and an available interval information indicating a
length of the available interval.

[0043] Preferably, the information on the cellbar bit, the information on
the low duty cycle (LDC) ID and the information on the low duty mode
pattern are obtained via one selected from the group consisting of a
deregistration command (AAI_DREG-CMD) message, a sleep response
(AAI_SLP-RSP) message, a ranging response (AAI_RNG-RSP) message, a
neighbor advertisement (AAI_NBR-ADV) message and a super frame header
(SFH) and wherein the selected one is transmitted by the femto base
station or a macro base station including the femto base station.

[0044] Preferably, the cellbar bit includes one selected from the group
consisting of a closed subscriber group cellbar bit indicating
availability or unavailability for a service for a random mobile station
according to a presence or non-presence of subscription of a closed
subscriber group and a femto cellbar bit indicating a presence or
non-presence of availability for a service to every mobile station.

[0045] Preferably, the low duty mode pattern is determined with reference
to at least one selected from the group consisting of a battery level, an
available resource status and a subscriber type of the femto base
station.

[0046] It is to be understood that both the foregoing general description
and the following detailed description are exemplary and explanatory and
are intended to provide further explanation of the invention as claimed.

Advantageous Effects of Invention

[0047] Accordingly, the present invention provides the following effects
or advantages.

[0048] First of all, using embodiments of the present invention, it is
able to minimize power consumption of a femto base station and
interference with a macro cell in a wireless access system supporting a
femtocell.

[0049] Secondly, using embodiments of the present invention, a different
low duty mode pattern is applied according to a type of a femto cell,
whereby an efficient low duty mode operation is enabled.

[0050] Thirdly, the present invention is efficient because a mobile
station is able to operate in a manner of being implicitly aware of a low
duty mode pattern of a femto base station via a super frame header or a
prescribed MAC message.

[0051] Fourthly, the present invention is efficient because a femto base
station determines a low duty mode pattern to follow in consideration of
its state such as a battery level, an available resource and the like.

[0052] It will be appreciated by persons skilled in the art that that the
effects that could be achieved with the present invention are not limited
to what has been particularly described hereinabove and other advantages
of the present invention will be more clearly understood from the
following detailed description taken in conjunction with the accompanying
drawings.

BRIEF DESCRIPTION OF DRAWINGS

[0053] The accompanying drawings, which are included to provide a further
understanding of the invention and are incorporated in and constitute a
part of this specification, illustrate embodiments of the invention and
together with the description serve to explain the principles of the
invention.

[0054] In the drawings:

[0055] FIG. 1 is a diagram of an example for a network structure including
a femto base station (FBS);

[0056] FIG. 2 is a diagram of one example for a low duty mode operation of
a femto base station according to one embodiment of the present
invention;

[0057] FIG. 3 is a diagram of another example for a low duty mode
operation of a femto base station according to one embodiment of the
present invention;

[0058] FIG. 4 is a diagram of a further example for a low duty mode
operation of a femto base station according to one embodiment of the
present invention;

[0059] FIG. 5 is a diagram of a relation between a type change and low
duty cycle of a femto base station according to one embodiment of the
present invention;

[0060] FIG. 6 is a diagram of one example for a low duty mode operation of
a femto base station according to another embodiment of the present
invention;

[0061] FIG. 7 is a diagram of one example for a femto base station
operation in correspondence with a battery level of a femto base station
according to another embodiment of the present invention;

[0062] FIG. 8 is a diagram of another example for a femto base station
operation in correspondence with a battery level of a femto base station
according to another embodiment of the present invention; and

[0063] FIG. 9 is a block diagram for an example of a transmitting and
receiving side structure according to another embodiment of the present
invention.

MODE FOR THE INVENTION

[0064] The present invention relates to a wireless access system.
Reference will now be made in detail to methods of efficient low duty
mode operation in a femto base station according to various embodiments
of the present invention, examples of which are illustrated in the
accompanying drawings.

[0065] Exemplary embodiments described hereinbelow are combinations of
elements and features of the present invention. The elements or features
may be considered selective unless otherwise mentioned. Each element or
feature may be practiced without being combined with other elements or
features. Further, an embodiment of the present invention may be
constructed by combining parts of the elements and/or features. Operation
orders described in embodiments of the present invention may be
rearranged. Some constructions of any one embodiment may be included in
another embodiment and may be replaced with corresponding constructions
of another embodiment.

[0066] In the description of drawings, procedures or steps, which may ruin
the substance of the present invention, are not explained. And,
procedures or steps, which can be understood by those skilled in the art,
are not explained as well.

[0067] In exemplary embodiments of the present invention, a description is
made of a data transmission and reception relationship between a BS and a
Mobile Station (MS). Herein, the term BS refers to a terminal node of a
network, which communicates directly with the MS. In some cases, a
specific operation described as performed by the BS may be performed by
an upper node of the BS.

[0068] Namely, it is apparent that, in a network comprised of a plurality
of network nodes including a BS, various operations performed for
communication with an MS may be performed by the BS, or network nodes
other than the BS. The term BS may be replaced with the term fixed
station, Node B, eNode B (eNB), access point, Advanced Base Station (ABS)
etc. The term MS may be replaced with the term User Equipment (UE),
Subscriber Station (SS), Mobile Subscriber Station (MSS), mobile
terminal, Advanced Mobile Station (AMS), etc.

[0069] A transmitter means a node that transmits voice or data service and
a receiver means a node that receives voice or data service. Hence, an MS
may be a transmitter and a BS may be a receiver, on an uplink. Likewise,
the MS may be a receiver and the BS may be a transmitter, on a downlink.

[0070] Meanwhile, the MS may be any of a Personal Digital Assistant (PDA),
a cellular phone, a Personal Communication Service (PCS) phone, a Global
System for Mobile (GSM) phone, a Wideband Code Division Multiple Access
(WCDMA) phone, a Mobile Broadband System (MBS) phone, etc.

[0071] Exemplary embodiments of the present invention may be achieved by
various means, for example, hardware, firmware, software, or a
combination thereof.

[0073] In a firmware or software configuration, the methods according to
the exemplary embodiments of the present invention may be implemented in
the form of a module, a procedure, a function, etc. performing the
above-described functions or operations. A software code may be stored in
a memory unit and executed by a processor. The memory unit is located at
the interior or exterior of the processor and may transmit and receive
data to and from the processor via various known means.

[0074] Exemplary embodiments of the present invention are supported by
standard documents disclosed for at least one of wireless access systems
including an Institute of Electrical and Electronics Engineers (IEEE) 802
system, a 3rd Generation Project Partnership (3GPP) system, a 3GPP Long
Term Evolution (LTE) system, and a 3GPP2 system. In particular, the steps
or parts, which are not described to clearly reveal the technical idea of
the present invention, in the embodiments of the present invention may be
supported by the above documents. All terminologies used herein may be
supported by at least one of P802.16-2004, P802.16e-2005, and P802.16Rev2
documents which are the standards of IEEE 802.16.

[0075] Specific terms used for the exemplary embodiments of the present
invention are provided to help the understanding of the present
invention. These specific terms may be replaced with other terms within
the scope and spirit of the present invention.

[0076] In the following description, a low duty mode of a femto base
station according to the present invention is explained.

[0077] First of all, a femto base station according to the present
invention can exist within a whole network, a coverage area of at least
one macro base station (MBS) or an area corresponding to a macro cell or
at least one paging group.

[0078] Secondly, a femto base station according to the present invention
can enter a low duty mode to save power and reduce interference with a
neighbor cell as well as a normal operation mode.

[0079] A low duty operation can include an available interval (AI) and an
unavailable interval (UAI). A role played by a femto base station in each
of the intervals is described as follows.

[0080] First of all, regarding the available interval, a femto base
station is able to activate a radio interface for paging, system
information transmission, ranging or data traffic transmission during the
available interval. In particular, the femto base station is able to
transmit a synchronization channel and/or super frame header (SFH) in
downlink during the available interval. Moreover, the femto base station
is able to monitor whether an access try, which is transmitted by a
mobile station, e.g., a ranging code transmission exists in a preset
uplink interval.

[0081] Secondly, regarding the unavailable interval, a femto base station
does not perform a transmission on a radio interface during the
unavailable interval. Through this, the femto base station alleviates
interference with an adjacent femto base station using the same frequency
or a macro base station as soon as reduces its power consumption.
Moreover, the femto base station performs synchronization with a macro
base station (overlay macro BS) including itself or is able to measure
interference from a neighbor cell.

[0082] For clarity and convenience, in this disclosure, one available
interval and one unavailable interval are named a low duty cycle.

[0083] In the following description, conditions for a femto base station
to enter the above mentioned low duty mode are explained.

[0084] First of all, a low duty mode entry condition of a femto base
station can be determined according to a presence or non-presence of a
mobile station operating in normal mode by being attached to the femto
base station. In particular, the femto base station is able to enter the
low duty mode if a mobile station connected to the femto base station
operates in idle or sleep mode or any mobile station fails to exist
within a service range of the femto base station.

[0085] In this case, sequences of the available and unavailable intervals
can for a low duty mode pattern (hereinafter abbreviated LDM pattern).
Specifically, repetition of one available interval and one unavailable
interval can becomes a default LDM pattern. In case that a femto base
station enters a low duty mode, a default LDM pattern of a corresponding
femto base station can be activated. In doing so, the femto base station
can have one or more default LDM patterns.

[0086] The following parameters can be contained in the default LDM
pattern. [0087] Available interval (AI): As a value indicating a length
of an available interval, the available interval is preferably set by a
unit of 4 frames. [0088] Unavailable interval (UAI): As a value
indicating a length of an unavailable interval, the unavailable interval
is preferably set by a unit of 4 frames as well. [0089] Start super frame
number: This indicates a number of a super frame with which a low duty
mode starts.

[0090] The default LDM pattern is pre-provisioned in a prescribed region
by a communication service provider or another subject, follows a format
of a broadcast message of a macro/femto base station, or is unicasted to
a mobile station by a femto base station.

[0091] In the following description, explained are messages for informing
a mobile station of an LDM pattern applicable to embodiments of the
present invention.

[0092] First of all, LDM pattern information is broadcasted to a mobile
station by a macro base station and/or a femto base station via SFH or a
neighbor advertisement (AAI_NBR-ADV) message or can be unicast via such a
message as a deregistration command (AAI_DREG-CMD), a sleep response
(AAI_SLP-RSP), a ranging response (AAI_RNG-RSP) and the like.

[0093] When the above mentioned messages are applied to embodiments of the
present invention, new fields for indicating LDM pattern information are
added. This is explained with reference to Table 1 as follows.

[0094] Table 1 shows one example for types of fields added to medium
access control (MAC) messages applicable to embodiments of the present
invention.

TABLE-US-00001
TABLE 1
Syntax Size(bit) Notes
AAI_XXX_Message_format( ) { -- --
~
FFI (Femto Frequency Information) Frequency bands
available for a
femto base station
LDC (Low Duty Cycle) information {
LDC information for CSG Closed
Femtocell BS {
Start Frame Frame Number or
Super frame number at
the timing point for a
femto BS to enter a
low duty mode
LDC (Low Duty Cycle) Interval for Femto BS
to operate in Low Duty
Mode therein
AI (Available Interval) This indicates an available
interval in the interval in
which Femto BS operates
in Low Duty mode.
Namely, during this
interval, an MS is able to
receive a preamble or
SFH sent by Femtocell
BS and is able to
transmit a signaling
message to Femtocell
BS in UL interval.
}
~
} //End of AAI_RNG-RSP

[0095] Referring to Table 1, a MAC message according to the present
invention can be configured in a manner that a femto frequency
information (FFI) field, a start frame field, a low duty cycle (LDC)
field and an available interval (AI) field are further added to a
message.

[0096] In this case, the start frame field is the field indicating a frame
number or a super frame number at a timing point for a femto base station
to operate in low duty mode. The low duty cycle field indicates a length
resulting from adding one available interval and one unavailable interval
in an LDM pattern of a femto base station together. And, the AI field
indicates a length of an available interval in a low duty cycle.

[0097] Meanwhile, the FFI filed is the field indicating a frequency band
used by a femto base station and its detailed format is described with
reference to Table 2 in the following.

[0098] Table 2 shows one example for types of the femto frequency
information field applicable to embodiments of the present invention.

TABLE-US-00002
TABLE 2
Type Length Value Scope
Enumerated(Band I, Band SFH, Additional system in-
II, Band III, Band IV, Band formation, AAI_NBR-ADV
VIII, Band IX, Band
X, Band XI, Band XII, Band
XIII, Band XIV, Band
XV, Band XVI, Band
XVII, Band XVIII, Band
XIX, Band XX, Band
XXI, Band XXII, extension
indicator)

[0099] Referring to Table 2, the FFI field represents a value of a band
used by a femto base station as one of 1 to 22 or can be set to an
extension indication value.

[0100] Meanwhile, according to embodiments of the present invention,
assume that a macro base station (overlay macro BS) and a femto base
station belonging thereto are synchronized with each other.

[0101] Embodiments of the present invention are described as follows.

First Embodiment

[0102] According to one embodiment of the present invention, provided is
an operating method in a different low duty mode pattern in
correspondence with a type of a femto base station according to a service
provided target (i.e., femto BS subscriber type). This is explained with
reference to FIG. 2 as follows.

[0103] FIG. 2 is a diagram of one example for a low duty mode operation of
a femto base station according to one embodiment of the present
invention.

[0104] Referring to FIG. 2, a femto base station operating in regular mode
and a femto base station of CSG open type do not enter a low duty mode.
And, a femto base station of a CSG closed type operates in a low duty
mode of a prescribed LDM pattern.

[0105] The CSG open femto base station grants an access of a mobile
station failing to subscribe a CSG (i.e., non-CSG member) to have a
property of an OSG femto base station. Thus, a low duty mode operation is
applied to the CSG closed femto base station only and may not be applied
to the CSG open femto base station to always grant an access to the
non-CSG member.

[0106] Meanwhile, it is able to help a mobile station to perform a
scanning process in a manner of synchronizing LDM pattern of every CSG
closed femto base station within a macro base station. In particular, in
order to search or detect a CSG closed femto base station, a mobile
station is able to scan CSG femto base stations in an available interval
using the previously acquired LDM pattern information of the CSG closed
femto base station. In other words, the mobile station is able to decode
a preamble and super frame header, which is transmitted by a femto base
station in an available interval of a low duty cycle indicated by the LDM
pattern information of the CSG closed femto base station, to scan the CSG
closed femto base stations.

[0107] According to another example of the present embodiment, a length of
an available length of a low duty cycle can be set different according to
a type of a femto base station. This is explained with reference to FIG.
3 as follows.

[0108] FIG. 3 is a diagram of another example for a low duty mode
operation of a femto base station according to one embodiment of the
present invention.

[0109] Referring to FIG. 3, according to another example of the present
embodiment, a low duty mode is basically applied to both a CSG closed
femto base station and a CSG open femto base station. Yet, as mentioned
in the foregoing description, since the CSG open femto base station
grants an access of a non-CSG member to have a property of an OSG femto
base station, the number of mobile stations attempting accesses to the
CSG open femto base station can be relatively greater than that of mobile
stations attempting accesses to the CSG closed femto base station.
Therefore, the present embodiment proposes that an available interval of
the CSG open femto base station is set longer than that of the CSG closed
femto base station, as shown in FIG. 3, while low duty cycles of the
femto base stations of the two types are maintained.

[0110] In this case, it is able to help a mobile station to perform a
scanning process in a manner of synchronizing LDM patterns of all the CSG
closed femto base stations within a macro base station with each other.
In particular, in order to search or detect CSG closed femto base
stations, the mobile station is able to scan CSG femto base stations in
an available interval using the previously acquired LDM pattern
information of the CSG closed femto base station. In other words, the
mobile station is able to decode a preamble and super frame header, which
is transmitted by a femto base station in an available interval of a low
duty cycle indicated by the LDM pattern information of the CSG closed
femto base station, to scan the CSG closed femto base stations.

[0111] According to a further example of the present embodiment, a ratio
of an available length included in a same time can be set different
according to a type of a femto base station. This is explained with
reference to FIG. 4 as follows.

[0112] FIG. 4 is a diagram of a further example for a low duty mode
operation of a femto base station according to one embodiment of the
present invention.

[0113] Referring to FIG. 4, while a length of an available interval is set
fixed, a low duty cycle of a CSG open femto base station can be set
shorter than that of a CSG closed femto base station. Alternatively, an
available interval of a CSG open femto base station can be set to occur
more frequently than that of a CSG closed femto base station within the
same interval. In particular, in FIG. 4, an available interval of such a
CSG open femto base station as a femto base station 2 and a femto base
station 3 can occur twice frequently than that of such a CSG open femto
base station as a femto base station 4 and a femto base station 5.
Accordingly, if LDM patterns of all the CSG closed femto base stations
within a macro base station are unified, a mobile station is able to scan
a CSG open femto base station in an available interval of a low duty
cycle of a CSG open femto base station, which is not overlapped with an
available interval of a default low duty cycle.

[0114] The above described LDM patterns of the types can be represented as
Math Figure 1 and Math Figure 2.

[0115] Referring to Math Figure 1, a low duty cycle of a CSG closed femto
base station is set equal to a default low duty cycle. Referring to Math
Figure 2, a low duty cycle of a CSG closed femto base station can be set
2-n times greater than that of a CSG closed femto base station. Hence,
the available interval is enabled to occur more frequently in the same
interval than that of the CGS closed femto base station. In this case, a
value of the n is delivered by being contained in LDM pattern information
transmitted by a macron base station or a femto base station. And, the
default low duty cycle means a low duty cycle of a default LDM pattern.

[0116] The n value proposed by the present invention can be included as a
format shown in Table 3 in one of MAC messages according to the present
invention together with the LDM pattern information.

TABLE-US-00003
TABLE 3
Syntax Size(bit) Notes
FFI (Femto Frequency Refer to Table 2
Information)
Default LDC
(Low Duty Cycle) in-
formation {
Start Frame Frame Number or Super frame
number at a timing point that
Femto BS enters a low duty mode
LDC (Low Duty Cycle) Interval for Femto BS to operate
in Low Duty Mode
AI (Available Interval) This indicates an available interval
in an interval for Femto BS to
operate in Low Duty mode. In
particular, MS is able to receive a
preamble or SFH transmitted by
Femto cell BS during this interval
and is able to send a signaling
message to a femto cell BS in UL
interval.
}
N Value applied to the following
Math Figure: 2-n * Default
Low Duty Cycle
}

[0117] Meanwhile, the CSG femto base station can change its type from a
CSG open type to a CSG closed type, and vice versa. And, the CSG femto
base station is able to change a low duty cycle correspondingly. This is
explained with reference to FIG. 5 as follows.

[0118] FIG. 5 is a diagram of a relation between a type change and low
duty cycle of a femto base station according to one embodiment of the
present invention.

[0119] Referring to FIG. 5, a femto base station of a CSG type according
to the present embodiment can change its low duty cycle to cope with a
change of a subscriber group type as well.

[0120] In particular, as a random CSG femto base station of a CSG open
type operates by a low duty cycle shorter than that of a CSG closed type
or a low duty cycle having an available interval included therein more
than that of the CSG closed type, if a state of the random CSG femto base
station is changed into the CSG closed type, it operates by a low duty
cycle (e.g., a default low duty cycle) corresponding to the CSG closed
type. Moreover, since a bit (e.g., a CSG cell bar bit) indicating a CSG
type can be included in a super frame header, if the CSG type is changed,
a corresponding bit can be changed into a value corresponding to the
changed type as well.

Second Embodiment

[0121] According to another embodiment of the present invention, a method
of informing a mobile station of an LDM pattern applied to a femto base
station implicitly is provided.

[0122] For this, after a prescribed number (e.g., N) of LDM patterns of a
femto base station has been defined, if the LDM pattern to be followed by
the femto base station is determined by such a scheme as Math Figure 3, a
mobile station can be implicitly aware of the determined LDM pattern.

MathFigure 3

LDM pattern=Femto BS ID modulo N [Math.3]

[0123] For instance, when the number of LDM patterns is 4 (i.e., N=4), if
a remainder is 1 as a result of applying modulo 4 on an identifier of a
corresponding femto base station, a mobile station can aware that the
femto base station operates in a low duty mode by applying a first LDM
pattern and is then able to perform scan on the corresponding femto base
station according to the first LDM pattern.

[0124] The N LDM patterns can be determined by a communication service
provider or a macro base station or can be determined as system
parameters. The macro base station or the femto base station is able to
transmit the N LDM patterns to a mobile station via a multicast or
unicast message.

[0125] Meanwhile, in a manner of defining a plurality of low duty cycle
IDs instead of the femto base station ID in Math Figure 3 and then
mapping a LDM pattern to each of the IDs, the LDM pattern to be applied
to a corresponding femto cell can be determined by Math Figure 4.

MathFigure 4

LDM pattern=Low Duty Cycle ID modulo N [Math.4]

[0126] This low duty cycle ID can be assigned to a mobile station by a
macro base station or a femto base station via one of AAI_NBR-ADV,
AAI_RNG-RSP, AAI_SLP-RSP, SFH and the like.

Third Embodiment

[0127] According to another embodiment of the present invention, a
different LDM pattern can be applied in correspondence with a state of a
femto base station. For example of a state variable of a femto base
station, there is a power state of a femto base station, i.e., a battery
level.

[0128] For this, the present embodiment proposes to define a battery level
threshold. The present embodiment also proposes to define an LDM pattern,
which will be applied if a battery level of a femto base station becomes
equal to or smaller than a preset battery level threshold, and an LDM
pattern, which will be applied if a battery level of a femto base station
becomes greater than the preset battery level threshold, in advance.

[0129] If so, a femto base station is able to operate in an LDM pattern
different according to its battery level threshold. This ex explained
with reference to FIG. 6.

[0130] FIG. 6 is a diagram of one example for a low duty mode operation of
a femto base station according to another embodiment of the present
invention.

[0131] Referring to FIG. 6, if a battery level of a femto base station
becomes equal to or smaller than a preset battery level threshold, the
femto base station is able to operate in an LDM pattern having an
available interval shorter (in this case, 1/2) than that of an LDM
pattern, which is applied if the battery level is greater than the
threshold, in the same interval to save power.

[0132] Yet, in this case, a method for informing a mobile station of the
LDM pattern changed according to the lowered battery level is necessary.
For this, the present embodiment proposes to use a CSG cellbar bit. As
mentioned in the foregoing description, the CSG cellbar bit can be
included in SFH. The application of the CSG cellbar bit is explained with
reference to FIG. 7 as follows.

[0133] FIG. 7 is a diagram of one example for a femto base station
operation in correspondence with a battery level of a femto base station
according to another embodiment of the present invention.

[0134] Referring to FIG. 7, assume that a mobile station 1 (AMS 1) is a
mobile station not subscribing a CSG (i.e., a non-CSG member) of a femto
base station. And, assume that a mobile station 2 (AMS 2) is a mobile
station having subscribed the CSG of the femto base station.

[0135] Each of the mobile stations receives a neighbor advertisement
(AAI_NBR-ADV) message from a macro base station and is then able to
acquire low duty pattern (cycle) information of a femto base station from
the received message [S701, S7021].

[0136] Afterwards, a battery level of the femto base station is lowered
equal to or smaller than a preset threshold [S703].

[0137] When a battery level of a CSG femto base station (CSG open type) is
lowered equal to or smaller than the threshold, the femto base station of
the CSG open type broadcasts the service unavailability to the non-CSG
member mobile stations via SFH in a manner of setting a CSG cellbar bit
to a specific value, e.g., 1 [S704].

[0138] If the battery level is lowered equal to or smaller than the
threshold, the CSG femto base station can operate in a low duty mode by
applying a low duty cycle used for the battery level equal to or smaller
than the threshold.

[0139] In this case, the AMS 1 failing to subscribe the CSG is restricted
from an access to the femto base station and is unable to perform such an
operation as a handover entry, an initial network entry and the like
[S705].

[0140] However, even if the CSG cellbar bit is set, accesses of the CSG
member mobile stations can be granted [S706].

[0141] In case of receiving the SFH in which the CSG cellbar bit is set,
the mobile station is able to scan the CSG femto base station using the
low duty cycle applied to the femto base station below the threshold.

[0142] The present embodiment is identically applicable to a case that the
resource of the CSG femto base station is exhausted as well as a case
that the battery level is lowered equal to or smaller than the threshold.

[0143] Table 4 shows one example for a format that LDM pattern information
applicable to the present embodiment is included in a neighbor
advertisement message.

TABLE-US-00004
TABLE 4
Syntax Size(bit) Notes
AAI_NBR-ADV_Message_format( ) { -- --
~
FFI (Femto Frequency Information) Refer to Table 2
LDC information for CSG
Femtocell BS
(Battery level > threshold) {
Start Frame Frame Number or Super
frame number at a timing
point that Femto BS
enters a low duty mode
LDC (Low Duty Cycle) Interval for Femto BS to
operate in Low Duty Mode
AI (Available Interval) This indicates an available
interval in an interval for
Femto BS to operate in
Low Duty mode. In
particular, MS is able to
receive a preamble or
SFH transmitted by
Femto cell BS during this
interval and is able to send
a signaling message to a
femto cell BS in UL
interval.
}
LDC information for CSG
Femtocell BS
(Battery level < threshold) {
Start Frame Frame Number or Super
frame number at a timing
point that Femto BS
enters a low duty mode
LDC (Low Duty Cycle) Interval for Femto BS
to operate
in Low Duty Mode
AI (Available Interval) This indicates an available
interval in an interval
for Femto BS to
operate in Low Duty
mode. In particular,
MS is able to receive a
preamble or SFH
transmitted by
Femto cell BS during
this interval
and is able to send
a signaling message to
a femto cell BS in UL
interval.
}
~
} //End of AAI_NBR-ADV

[0144] Referring to Table 4, different LDM pattern information can be
included in each MAC message according to a relation between a battery
level and a threshold.

[0145] Information on two LDM patterns can be simultaneously included in a
MAC message, as shown in Table 4. Yet, it is able to use a method of
changing LDM pattern information each time a value of a CGS cellbar bit
is toggled according to a battery level, as shown in Table 5.

TABLE-US-00005
TABLE 5
Syntax Size(bit) Notes
AAI_NBR-ADV_Message_format( ) { -- --
~
FFI (Femto Frequency Information) Refer to Table 5
LDC (Low Duty Cycle) information {
LDC information for CSG Femtocell BS
{
Start Frame Frame Number or Super
frame number at a
timing point that
Femto BS enters
a low duty mode
LDC (Low Duty Cycle) Interval for Femto BS
to operate
in Low Duty Mode
AI (Available Interval) This indicates an
available interval
in an interval for Femto
BS to operate in Low
Duty mode. In
particular, MS is able
to receive a
preamble or SFH
transmitted by
Femto cell BS during
this interval
and is able to send
a signaling
message to a femto
cell BS in UL
interval.
}
~
} //End of AAI_NBR-ADV

[0146] Namely, two kinds of LDM pattern information such as LDM pattern
information in case of a battery level equal to or greater than a
threshold and LDM pattern information in case of a battery level smaller
than a threshold can be delivered as shown in Table 4. Yet, one LDM
pattern information, as shown in Table 5, can be transmitted to a mobile
station. In particular, in case that a battery level of a femto base
station is lowered from a level equal to or greater than a threshold to a
level below the threshold or is raised again above the threshold, a CGS
cellbar bit included in SFH is toggled. Simultaneously, a mobile station
is able to acquire information on the changed LDM pattern from
AAI_NBR-ADV message.

[0147] In the description with reference to FIG. 7, the LDM pattern
information is delivered via the AAI_NBR-ADV message, which is exemplary
and by which the present invention is non-limited. Alternatively, the LDM
pattern information can be delivered to a mobile station via a message
(AAI_DREG-CMD, AAI_SLP-RSP, AAI_RNG-RSP, AAI_NBR-ADV, etc.) unicasted by
a femto/macro base station or a message (SFH, AAI_NBR-ADV, etc.)
broadcasted by a femto/macro base station.

[0148] FIG. 8 is a diagram of another example for a femto base station
operation in correspondence with a battery level of a femto base station
according to another embodiment of the present invention.

[0149] FIG. 8 is another example for the present embodiment described with
reference to FIG. 7. FIG. 8 is applicable to every femto base station
(i.e., all femto base station irrespective of a subscriber type) except a
CSG femto base station. Accordingly, a cellbar bit is preferably changed
into a femto cellbar bit from a CSG cellbar bit.

[0150] Referring to FIG. 8, a mobile station 1 (AMS 1) and a mobile
station 2 (AMS 2) are able to receive LDM pattern information of a femto
base station from a macro base station [S801, S802].

[0151] Afterwards, when a battery level of a femto base station is lowered
equal to or smaller than a prescribed threshold, the femto base station
broadcasts the service unavailability to mobile stations via SFH in a
manner of setting a femto cellbar bit to a specific value, e.g., 1 [S803,
S804].

[0152] If the battery level is lowered equal to or smaller than the
threshold, the femto base station can operate in a low duty mode by
applying a low duty cycle used for the battery level equal to or smaller
than the threshold.

[0153] Accordingly, each of the mobile stations may not perform a request
for handover or initial network entry into the corresponding femto base
station [S805, S806].

[0154] Yet, in case of receiving the SFH in which the femto cellbar bit is
set, the mobile station is able to scan the corresponding femto base
station by applying the low duty cycle used below the threshold.

[0155] The present embodiment is identically applicable to a case that the
resource of the CSG femto base station is exhausted as well as a case
that the battery level is lowered equal to or smaller than the threshold.

[0156] Moreover, like the case shown in FIG. 7, in case of FIG. 8, a base
station is able to deliver two kinds of LDM pattern information such as
LDM pattern information in case of a battery level above threshold and
LDM pattern information in case of a battery level below threshold, as
shown in Table 4, via a neighbor advertisement message. Alternatively,
the base station is able to deliver one LDM pattern information, as shown
in Table 5, to a mobile station only. In particular, in case that a
battery level of a femto base station is lowered from a level equal to or
greater than a threshold to a level below the threshold or is raised
again above the threshold, a femto cellbar bit included in SFH is
toggled. Simultaneously, a mobile station is able to acquire information
on the changed LDM pattern from AAI_NBR-ADV message.

[0157] Table 6 partially shows a format of SFH transmitted by a CGS femto
base station in the embodiment shown in FIG. 7. Table 7 partially shows a
format of SFH transmitted by a femto base station in the embodiment shown
in FIG. 8.

[0158] Referring to Table 6, a mobile station can be aware whether a
corresponding femto base station grants a CSG member mobile station only
or a CSG non-member mobile station an access, via a value of a CSG
cellbar bit included in SFH of a CSG femto base station.

[0159] Referring to Table 7, a mobile station can be aware whether a
corresponding femto base station grants every mobile station an access or
does not grant any mobile station an access, via a value of a femto
cellbar bit included in SFH of the femto base station.

[0160] Meanwhile, a femto base station status report (AAI_STS-REP)
message, as shown in Table 8 or Table 9, is newly defined. A femto base
station is then able to transmit a cellbar bit (e.g., CSG cellbar bit or
femtocell cellbar bit) and LDM pattern information to a mobile station.

[0161] Table 8 partially shows a format of a status report message
transmitted by a CGS femto base station in the embodiment shown in FIG.
7. Table 9 partially shows a format of a status report message
transmitted by a femto base station in the embodiment shown in FIG. 8.

[0162] Referring to Table 8 and Table 9, the above described cellbar bit
and the LDM pattern information are transmitted to a mobile station in a
manner of being included in the status report message.

[0163] According to another example for a further embodiment of the
present invention, a method of supporting a low duty mode operation of a
femto base station using a low duty cycle ID (i.e., LDC ID) is provided.

[0164] A femto base station delivers a low duty cycle ID to a mobile
station to enable to implicitly recognize an LDM pattern of a
corresponding femto base station according to the low duty cycle ID. For
instance, according to a battery level or an available resource status, a
plurality of LDC IDs are defined in advance. Low duty cycles can be then
mapped to the defined LDC IDs, respectively.

[0165] A femto base station operates in a low duty mode by applying an LDM
pattern defined according to its battery level or an available resource
status and informs a mobile station of an LDC ID. Therefore, the mobile
station is enabled to be aware that the femto base station performs the
low duty mode with a specific LDM pattern.

[0166] The mobile station is able to scan the corresponding femto base
station using the LDM pattern mapped to the LDC ID transmitted by the
femto base station.

[0167] The LDC ID can be delivered to the mobile station via a message
(AAI_DREG-CMD, AAI_SLP-RSP, AAI_RNG-RSP, AAI_NBR-ADV, etc.) unicasted by
a femto/macro base station or a message (SFH, AAI_NBR-ADV, etc.)
broadcasted by a femto/macro base station.

[0168] Structures of Mobile Station and Base Station

[0169] In the following description, a mobile station and base stations
(FBS, MBS) according to another embodiment of the present invention for
implementing the above described embodiments of the present invention are
explained.

[0170] First of all, a mobile station works as a transmitter in uplink and
is able to work as a receiver in downlink. A base station works as a
receiver in uplink and is able to work as a transmitter in downlink. In
particular, each of the mobile station and the base station can include a
transmitter and a receiver for transmission of information and/or data.

[0171] Each of the transmitter and the receiver can include a processor, a
module, a part and/pr a means for performing embodiments of the present
invention. In particular, each of the transmitter and the receiver can
include a module (means) for encrypting a message, a module for
interpreting the encrypted message, an antenna for transceiving the
message and the like. Examples of these transmitting and receiving sides
are explained with reference to FIG. 9 as follows.

[0172] FIG. 9 is a block diagram for an example of a transmitting and
receiving side structure according to another embodiment of the present
invention.

[0173] Referring to FIG. 9, a left side shows a structure of a
transmitting side and a right side shows a structure of a receiving side.
The transmitting/receiving side can include an antenna 5/10, a processor
20/30, a transmitting (Tx) module 40/50, a receiving (Rx) module 60/70
and a memory 80/90. Each of the elements can perform a corresponding
function. The respective elements are explained in detail as follows.

[0174] First of all, the antenna 5/10 performs a function of transmitting
a signal generated by the Tx module 40/50 externally or a function of
receiving a radio signal externally and then delivering the received
radio signal to the Rx module 60/70. If MIMO function is supported, at
least two antennas can be provided.

[0175] The antenna, Tx module and Rx module can configure a radio
communication (RF) module.

[0176] The processor 20/30 controls overall operations of the transmitting
or receiving side in general. For instance, the processor 20/30 can
perform a controller function for performing the above described
embodiments of the present invention, a MAC (medium access control) frame
variable control function, a handover function, an authentication
function, an encryption function and the like.

[0177] In particular, a processor of a mobile station can acquire at least
one of LDM pattern information, cellbar bit information and low duty
cycle (LDC) ID of a femto base station via a unicasted message or
broadcasted information from the femto base station or a macro base
station by controlling a wireless communication module.

[0178] In this case, the broadcasted information can have a format of SFH
or AAI_NBR-ADV message. And, the unicasted message can include one of
AAI_DREG-CMD, AAI_SLP-RSP, AAI_RNG-RSP, AAI_STS-REP and the like.
Moreover, the cellbar bit information can include a CSG cellbar bit or a
femto cellbar bit.

[0179] Using the acquired information, the processor of the mobile station
determines the LDM pattern of the femto base station explicitly or
implicitly and is then able to scan the femto base station in an
available interval of a low duty cycle of the corresponding femto base
station.

[0180] Meanwhile, a processor of a femto base station interprets a MAC
message or data received from a mobile station, allocates an uplink
resource necessary for the mobile station, generates an uplink grant for
informing the mobile station of the allocation history and the like, and
is then able to perform scheduling for transmitting the uplink grant and
the like.

[0181] In particular, when the processor of the femto base station
determines that mobile stations attached to itself enter sleep mode or
idle mode or determines that any mobile station does not exist around
itself, it is able to determine to enter a low duty mode. Accordingly,
the processor determines a low duty mode pattern in which it will operate
and is then able to repeat a prescribed-length available interval
operation and a prescribed-length unavailable interval operation
according to the determined low duty more pattern. In doing so, the
processor is able to consider its subscriber type, battery level,
available resource status and the like in determining the low duty mode
pattern the processor will perform. The processor sets a cellbar bit of a
type suitable for the determined low duty mode pattern. The processor is
able to control information on the corresponding pattern to be
transmitted to a mobile station via a unicasted message or broadcast
information. The processor delivers the information on the corresponding
pattern to a macro base station and enables its LDM pattern information
to be included in a neighbor advertisement message that is going to be
broadcasted by the macro base station.

[0182] The Tx module 40/50 performs prescribed coding and modulation on
data, which is scheduled to be externally transmitted by the processor
20/30, and is then able to deliver the coded and modulated data to the
antenna 10/5.

[0183] The Rx module 60/70 reconstructs a radio signal externally received
via the antenna 5/10 into original data by performing decoding and
demodulation on the radio signal and is then able to deliver the
reconstructed original data to the processor 20/30.

[0184] A program for processing and control of the processor 20/30 can be
stored in the memory 80/90. And, the memory 20/30 can perform a function
for temporary storage of inputted/outputted data (e.g., sleep mode
information according to reference synchronization information, etc.).
Moreover, the memory 80/90 can include at least one storage medium of
such a type as a flash memory type, a hard disk type, a multimedia card
micro type, a card type of memory (e.g., SD memory, XD memory, etc.), a
Random Access Memory (RAM) type, an SRAM (Static Random Access Memory
type), a Read-Only Memory (ROM) type, an EEPROM (Electrically Erasable
Programmable Read-Only Memory) type, a PROM (Programmable Read-Only
Memory) type, a magnetic memory type, a magnetic disc type, and optical
disc type, and the like.

[0185] Meanwhile, a base station uses at least one of the above mentioned
modules to perform a controller function for performing the
above-described embodiments of the present invention, an OFDMA
(orthogonal frequency division multiple access) packet scheduling, TDD
(time division duplex) packet scheduling and channel multiplexing
function, a MAC (medium access control) frame variable control function
according to a service characteristic and electric wave environment, a
fast traffic real-time control function, a handover function, an
authentication and encryption function, a packet modulation/demodulation
function for data transmission, a fast packet channel coding function, a
real-time modem control function and the like or can further include
separate means, modules and/or parts for performing these functions.

INDUSTRIAL APPLICABILITY

[0186] Accordingly, the present invention is applicable to various
wireless access systems.

[0187] While the present invention has been described and illustrated
herein with reference to the preferred embodiments thereof, it will be
apparent to those skilled in the art that various modifications and
variations can be made therein without departing from the spirit and
scope of the invention. Thus, it is intended that the present invention
covers the modifications and variations of this invention that come
within the scope of the appended claims and their equivalents. Moreover,
claims failing to be explicitly cited in-between are combined to
construct new embodiments or can be included as new claims by Amendment
after filing the application.

Patent applications by Gi Won Park, Gyeonggi-Do KR

Patent applications by Jin Lee, Gyeonggi-Do KR

Patent applications by Ki Seon Ryu, Gyeonggi-Do KR

Patent applications by Yong Ho Kim, Gyeonggi-Do KR

Patent applications in class Zoned or cellular telephone system

Patent applications in all subclasses Zoned or cellular telephone system